It is known to construct a dart board with each separately scoring section of the board being of electrically conductive material and being insulated from adjacent sections. In a prior detection arrangement, the sections are respectively sequentially connected to a radio transmitter and the wire grid delineating the sections is arranged as a receiving aerial. When a dart is embedded in and at the same time partially projects from one section--also known as a "dart bed"--the dart acts as an aerial and the signal received at the time appropriate to connection of that bed is received more strongly at the grid. Thus the particular bed in which the dart is partially embedded can be determined from the timing of the higher level of received signal.
This arrangement suffers from the disadvantage that the received signal can vary greatly in accordance with the position of the dart in the bed. If the dart is in the middle of the bed, the signal is comparatively small; whereas if the dart is adjacent the grid, the signal is comparatively much larger.
European Patent No. 121,550 describes and claims: "A target apparatus comprising a target adapted to have a projectile thrown at it, and an associated automatic scoring arrangement, the target being divided into a plurality of separate beds each associated with a predetermined score that can be obtained by a player or sportsman causing a projectile to hit that bed, characterised in that the target is adapted to have a projectile at least partly made of electrically conductive material partially embedded therein with part of the projectile protruding from the target, each bed incorporating electrically conductive means for applying an electrical signal which is specific to that bed to a projectile embedded .in said bed, the apparatus further including an aerial or antenna for receiving electromagnetic radiation radiating from part of a projectile protruding from a bed, and means responsive to a received signal for determining the score attributable to the projectile from which the radiation is emanating."
It has been proposed that the arrangement of the beds as transmitters and the wire grid as receiver should be reversed with the beds being receivers and the grid being the transmitter. Such a reversal does not improve the basic problem of wide variation in received signal strength with dart position.
European Patent Application No. 181,420 described: "A target apparatus comprising a target of the type into which a projectile of conductive material may be embedded with part of the projectile still protruding from the target, and an associated automatic scoring arrangement, the target being divided into a plurality of separate mutually insulated beds each associated with a predetermined score that can be obtained by a player or sportsman causing a projectile to become embedded in that bed, and an aerial or antenna transmitting electromagnetic radiation which can be received by a part of a projectile protruding from a bed, each bed incorporating electrically conductive means for leading any signal present on the bed to means for determining the score attributable to the projectile, embedded in the bed, which is receiving the radiation."